JP2839019B2 - Method for manufacturing semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing a semiconductor device using a lead frame or a film carrier semiconductor device.

[0002]

2. Description of the Related Art In recent years, with the increase in integration and the number of functions of integrated circuit elements (hereinafter referred to as IC elements), the number of input / output terminals and the pitch of electrodes of IC elements have been reduced. For example, there is an IC element having a square area of 6 to 12 nm and an input / output terminal of about 300 to 600 pins. In a general wire bonding method, since the inner lead pitch of the lead frame used is at least about 200 μm,
When the C element is small and the number of input / output terminals is large, the length of the bonding wire becomes long, for example, 6 to 10 nm, and it is difficult to manufacture due to disconnection or short-circuit between wires caused by wire flow during resin encapsulation. It has become.

Therefore, attention has been paid to a semiconductor device in which an outer lead bonding lead (OLB lead) of a film carrier semiconductor device (hereinafter referred to as a TAB type semiconductor device or simply TAB) is bonded to an inner lead of a lead frame. Generally, such a TAB type semiconductor device is constituted by a quad flat package (QFP), and is hereinafter referred to as a TABin QFP type semiconductor device. In this TABinQFP semiconductor device, so-called outer lead bonding (hereinafter referred to as OLB) for connecting the OLB lead of the TAB to the inner lead of the lead frame is performed by a batch bonding method. Excellent productivity. Further, the TAB lead corresponding to the bonding wire of the wire bonding method is fixed on the tape, so that no problem occurs at the time of sealing the resin.

In a specific conventional manufacturing method, as shown in FIG. 9 (a), after the OLB lead 4 of the TAB type semiconductor device previously connected to the IC element 1 is aligned with the inner lead 11 of the lead frame, As shown in FIG.
The IC element 1 is disposed on a bonding stage 28 and is connected by plating 29 by a thermocompression method in which heat and pressure are applied to a connection portion by a heated thermocompression tool 27.

Japanese Patent Laid-Open Publication No. 2-28043 describes a method in which the structure is the same, but the purpose is to prevent the breakage of the outer leads, which is likely to occur when a package is composed of TAB alone. Figure 1
0 is shown. As shown in FIG. 10, the semiconductor chip 1 is located in the device hole of the TAB film 5, and the inner leads 11 and the semiconductor chip 1 are connected. Further, after the front ends of the outer leads 12 of the lead frame are aligned so as to partially overlap the inner leads 11, the inner leads 11 and the outer leads 12 are joined by joining means such as welding or soldering. is there. In this case, after the resin sealing, the resin sealing portion 1 is formed.
The outer leads 12 protruding from the base 9 have strength and are not easily bent, and breakage does not occur.

[0006]

The conventional TAB described above.
Since the outer lead bonding of the inQFP type semiconductor device uses the thermocompression bonding method or the eutectic method, gold (Au), tin (S
n), plating of solder (Pb / Sn) or the like is required, and these plating layers are also required on the surface of the inner lead of the lead frame. Therefore, as compared with a semiconductor device in which other leads are drawn out of the package and used as outer leads, that is, a lead frame in which the surface of the inner leads is plated and the outer lead bonding step described above are compared with a case where the package is composed of TAB alone. Is added, so that there is a problem that the manufacturing cost is increased about 1.5 to 2 times. Although the use of a lead frame without plating treatment reduces the manufacturing cost, it requires development of a new OLB process.

[0007] When OLB is performed by resistance welding, the connection principle is based on the electric resistance of the metal to be welded and the contact resistance at the boundary, and the Joule heat generated by these resistances when current I is passed. Then, the metals in a state where the pressure P is applied are welded to each other. Therefore, the OLB operation can be performed collectively, that is, in a so-called gang system without providing a plating layer of silver or the like on the surface of the inner leads 11 of the lead frame 15. When a large number of OLB leads and inner leads are simultaneously resistance-welded by a gang system, it is necessary to make the contact area of the leads in each OLB portion uniform.

Generally, in a hermetically sealed package made of metal,
A projection is provided on the cap to ensure the stability of the resistance welding, but the projection of the cap of this type of package is formed in a linear pattern on the welding surface. Also, in the case of multi-point collective connection, it is necessary to make the contact area of the leads uniform, to make the amount of current flowing to each point uniform, and to make the connected portions uniform in connectivity. If the resistance is not maintained, the amount of current will differ depending on the contact condition, and a problem will occur such that a blown part and a non-connected part are mixed at the time of batch welding. In order to make the connection area of the leads of the OLB portion uniform, a fine OL
It is most useful to form fine protrusions on the B lead by plating, etching, pressing or the like.

Further, in the case where the joining method by welding is used in the manufacturing method of performing OLB by welding according to FIG. 10, a specific method is not specified, so that the outer lead 1 is not provided.
The surface treatment method and the type and method of welding of the inner lead 2 and the inner lead 11 are unknown, and it cannot be said that the joining means that can be actually applied has been sufficiently studied.

On the other hand, when the plating treatment is not performed by the thermocompression bonding method and the OLB lead OLB is attached to the TAB on the inner lead of the lead frame covered with the organic film for preventing oxidation, the organic film is heated by heating in a non-oxidizing atmosphere. Removed to expose the new surface of the lead frame material, and immediately bonded by thermocompression bonding.
Good connection is obtained by the B-lead diffusion reaction. If the inner lead of the lead frame is not plated, an oxide film is generated over time in the bare state as it is, and once this oxide film is formed, it is difficult to remove the oxide film. Deteriorate. Also, if an organic film is formed as an antioxidant treatment, oxidation of the lead frame can be prevented, but if it is used as it is, the bonding property will be significantly degraded and the connection resistance will be increased. If the film is removed by heat treatment immediately before the OLB and the OLB is performed by thermocompression bonding, no capital investment is required, and a lead frame that has not been plated can be used.

An object of the present invention is to provide a method of manufacturing a film carrier semiconductor device which is excellent in mass production, has a low manufacturing cost, and has an excellent fixing strength.

[0012]

According to the present invention, a TAB is provided.
In a method of manufacturing a semiconductor device in which an OLB lead of a die-shaped semiconductor device is subjected to OLB on an inner lead of a lead frame, the OLB lead is brought into contact with the inner lead, and the OLB is performed by an electric resistance welding method.

Further, the present invention provides a method of manufacturing a semiconductor device in which an OLB is applied to an inner lead of a lead frame in which an OLB lead of a TAB type semiconductor device is covered with an organic film. , OL
Performing OLB on the B lead by a thermocompression bonding method.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to the drawings. FIG. 1 is a plan view of the semiconductor device according to the first embodiment of the present invention in the order of manufacturing steps, and FIG.
It is sectional drawing of the manufacturing process order along XX of (b).
A TAB tape generally has a two-layer structure or a three-layer structure. Here, a case of a TAB tape having a three-layer structure will be described. As shown in FIG. 1A, a sprocket hole 7 for transport and positioning, a device hole 8 in which the IC element 1 enters, and four outer leads around the device hole 8 are placed on an insulating film carrier tape 6 such as polyimide. Bonding hole 9 (hereinafter referred to as OLB hole 9)
Respectively) are formed. Device hole 8 and OL
The insulating film carrier tape 6 between the B hole 9 becomes the suspender 5. Further, a metal foil such as copper is adhered on the insulating film 6 and is etched to form a plurality of leads having a desired shape.

Here, the leads formed on the film carrier tape will be referred to as TAB leads.
A plating layer of gold, tin or the like is formed on the surface of this TAB lead, but without forming a plating layer, for example,
The material such as copper may be used as it is. The portion of these leads outside the portion bonded to the suspender 5 is referred to as the OLB lead 4, and the portion projecting toward the device hole 8 from the portion bonded to the suspender 5 is referred to as ILB lead.
The LB lead 3 is used, and the tip of the ILB lead 3 is used as an inner lead bonding (ILB) unit 16. At the tip of the OLB lead 4, a pad 10 for electrical sorting is formed.

This ILB section 16 is connected to the electrode 2 formed on the IC element 1. When the electrode 2 is a bump made of gold or the like formed on the surface of the metal electrode of the IC element 1, it is connected by a gang-type thermocompression bonding method or the like. When the electrode 2 is formed of a pad made of aluminum or the like, for example, a single point inner lead bonding method using ultrasonic waves is used. In this way, so-called inner lead bonding for connecting the ILB portion 16 of the TAB lead and the electrode 2 of the IC element 1 is performed.

Thereafter, an electrical connection is made to the pad 10 from the outside, so that the I
An electrical selection and a BT test are respectively performed on the C elements 1. Then, O is used at the position of the OLB hole 9 using a mold.
The LB leads 4 are cut, the carrier tape 6 between the adjacent OLB holes 9 is cut, and the TAB type semiconductor device including the IC element 1, the TAB leads, the suspender 5, and the like is separated from the carrier tape 6. In the case of a large number of pins having a large number of leads, the dispersion of the leads can be prevented by leaving the suspender 5 adhered to the plurality of leads.

Next, the TAB lead is bent and formed, and as shown in FIG. 2A, the ILB lead 3 is provided between the portion of the lead adhered to the suspender 5 and the ILB lead 3.
The portion between the B lead 3 and the ILB portion 16 and the portion of the lead bonded to the suspender 5 and the OLB lead 4 are bent. The tip of the OLB lead 4 is also bent to form an outer lead bonding (OLB) portion 14. By performing this molding, the ILB portion 16 and the OLB portion 14 are maintained at substantially the same height, and the TAB lead in the portion adhered to the suspender 5 has a greater height than the ILB portion 16 and the OLB portion 14. The shape is maintained by the information. Since the thermal expansion coefficient of the sealing resin is larger than the thermal expansion coefficient of the lead, a gap is easily generated between the sealing resin and the lead due to a change with time.
This problem can be solved by bending the lead as described above and performing resin sealing with the lead having a margin.

The OLB 14 has a lead frame 1
A protrusion 17 which is a feature of the present invention is provided so as to make the contact area with the protrusion 5 uniform. This projection 17 is OLB
Before the leads 4 are cut, they are formed by plating or etching. FIG. 3 shows a case where the projections 17 are formed by this plating method. First, OLB lead 4 (FIG. 3)
A resist 23 is applied to (a)), and exposure and development are performed to open a projection forming portion (FIG. 3 (b)). The OLB lead 4 thus treated is partially plated with copper, gold, or the like (FIG. 3C). After this, resist 2
3 is removed (FIG. 3D), and the protrusion 17 can be formed by bending as shown in FIG. 3E.

In the case of forming by an etching method,
As shown in FIG. 4A, the resist 24 is used at the tip portion, and the OLB lead 4 is partially etched.
(B) The projections 17 are formed, the resist 23 is removed (FIG. 4C), and a tip is formed. Further, after the OLB lead is cut, it is formed by a press working method as shown in FIG. By using the molding dies 25 and 26 which are formed on each side of the OLB lead 4 as shown in FIG. 5A so that the projections 17 are formed at desired portions of the OLB lead 4 in advance.
A projection 17 as shown in FIG. 5B can be formed.

The desirable shape of the projection 17 is shown in FIG.
In the case of (a), the height t2 of the projection 17 is OLB.
The height of the projection 14 is equal to or greater than t1, and the diameter φ of the projection 17 is 0.
8 × W1 (the width of the OLB portion 14) or less, and FIG.
In such a case, it is sufficient that the height t3 of the projection 17 is not less than t1 and the width W2 of the projection 17 is 0.25 × W1. By satisfying these relationships, the projections 17 that reliably contact the inner leads 11 can be formed at low cost.

Next, as shown in FIG.
Is mounted on the island 1 of the lead frame 15. As a material of the lead frame 15, a copper alloy, an iron-nickel alloy, or the like is used. As shown in FIG. 1A, the island 13 of the lead frame 15 has been pushed up to a position lower than the lead portion of the lead frame 15 in advance. Next, the TAB IC element 1 and the suspender 5 are vacuum-adsorbed and conveyed above the island 13, and the back surface of the IC element 1 is adhered to the island 13 on which the adhesive 17 such as a silver paste is applied. Where I
The C element 1 is fixed to the island 13 such that the OLB portions 14 of the TAB leads are respectively located above the inner leads 11 of the lead frame.

Next, the connection between the OLB portion 14 of the OLB lead 4 and the inner lead 11 of the lead frame, that is, so-called outer lead bonding is performed. In this outer lead bonding, the OLB portion 11 of the OLB lead 4 to be welded and the inner lead 5 of the lead frame 18 are sandwiched between the gang welding electrodes 20 and 21 as shown in FIG. Fixed. At this time, the welding electrode portions 20 and 21 sandwich the projection 17 formed on the OLB portion 14, and the IC element 1, the suspender 5, the island 7, and the like are held by hollow portions inside the welding electrodes 20 and 21. You. Since the surfaces of the welding electrode portions 20 and 21 are flat and a load can be evenly applied to a portion to be welded, it is possible to prevent the lead from being cut due to a concentrated load.

Next, as shown in FIG. 7A, after a pressure P is applied to a portion to be welded, a current I
Then, the OLB portion 11 of the OLB lead 4 and the inner lead 5 of the lead frame 18 are welded by Joule heat. In this case, since welding is performed by Joule heat generated by applying a current to the electrodes 20 and 21, the surface of the inner leads 11 of the lead frame 18 can be collectively so-called without providing a plating layer of silver or the like. The outer lead bonding operation can be completed by the gang system. Further, since heat is generated around the uniformly shaped protrusions formed in the OLB portions, the welding is uniformly performed in all the OLB portions 14 even in the gang system. Specifically, the welding electrodes 20, 21 are made of, for example, tungsten (W). For example, the lead width of the OLB lead 4 is 0.065 mm, and the inner lead 1 of the lead frame is
In the case where the width of 1 is 0.125 mm, the number of OLB leads 4 is 240 pins, the conditions for outer lead bonding are as follows: pressure per lead P1 = 1 to ² kg / cm ² ,
A good outer lead bonding connection could be obtained by welding with a current I of 6000 to 9000 angstroms and a conduction time t of 0.1 to 0.2 seconds.

At the time of resistance welding by energization between the tools, the IC element 1 is connected to a portion to be welded via a TAB lead. However, the welding electrodes 20,
In the flow path of the current I between the flow path 21 and the flow path to the I element 1, the flow path between the welding electrodes 20 and 21 has much lower resistance, so that no current flows to the IC element 1. Therefore, there is no adverse effect on the IC element 1 due to the resistance welding.

In order to obtain a good OLB connection,
The thickness of the OLB lead 4 after the OLB is 4 times the thickness before the OLB.
It is necessary to adjust the current value so as to be in the range of 0 to 70%. This is because the thickness of the OLB lead 4 after the OLB is
If the thickness is 70% or more before, the connection strength is weak due to insufficient melting, and there is a possibility that the open defect of the OLB lead peels off at the time of encapsulation. In this case, the neck portion of the lead is weakened, and there is a possibility that the open defect of the OLB lead breakage may occur at the time of sealing.

Next, as shown in FIG. 7B, resin sealing is performed with a thermosetting resin 19 such as an epoxy resin. Then, the outer leads 12 of the lead frame 15 are
For example, a plating process such as soldering to the outside, a cutting of the outer lead portion from the lead frame 15, a forming into an L shape (gull wing shape) or a J shape according to the external lead shape of the package are performed. Thus, the tip of the inner lead portion formed from the TAB lead and the lead frame 15 are formed.
The TABinQFP type semiconductor device having the lead connected to the tip of the outer lead portion formed by welding is completed.

In the method of manufacturing a TABinQFP type semiconductor device described above, plating of the surface of the inner lead 11 of the lead frame 15 is not required.
0-30% cost reduction,
It can be manufactured at low cost. Further, since it is not necessary to plate the connection portion, there is no concern about occurrence of defects due to plating such as migration of silver, and a highly reliable package structure can be obtained.

FIG. 8 is a cross-sectional view illustrating a second embodiment of the present invention in the order of manufacturing steps. First, through steps similar to those shown in FIG. 1, a TAB type semiconductor device including the IC element 1, the leads of the TAB, the suspender 5, and the like is formed. Next, in the present embodiment, first, FIG.
As described above, only the inner lead 11 of the lead frame is placed on the bonding stage 28 and the thermocompression bonding tool 27 is pressed to apply heat. As a result, the organic film that has prevented the plating from being oxidized is thermally decomposed and removed. Next, FIG.
As described above, the TAB IC element 1 is fixed on the island 13 of the lead frame 15 with the adhesive 17. The IC element 1 is fixed to the island 13 such that the OLB portions 14 of the TAB leads are respectively located above the inner leads 11 of the lead frame. Then, the inner lead 11 of the lead frame 15 and the TAB OL
B section 14 and bonding stage 2
8 and thermocompression bonding tool 27, inner lead 11 and OL
A pressure P and a temperature are applied as shown in FIG. By applying the pressure P and the temperature, the inner lead 11 and the OLB portion 14 are collectively pressed and bonded together.

The method of removing the organic film for preventing the oxidation of the inner lead 11 of the lead frame by using the thermocompression bonding tool 26 and immediately bonding the inner lead 11 and the OLB portion 14 by thermocompression is a conventional method of transporting. An OLB bonder having a system and a recognition system can be used.

For example, the lead pitch of the OLB lead 4 is 0.35 mm, and the lead width of the OLB lead 4 is 0.065.
mm, the number of the OLB leads 4 is 240 pins, and the organic film of polyvinyl chloride is 0.003 mm on the surface of the inner lead 11 of the lead frame 15.
Pressure P = 10-20Kg, Tool temperature 400-500
The organic film is thermally decomposed under the conditions of ° C. and a time of 0.5 to 1.0 second.

The conditions for the outer lead bonding of the thermal bonding are as follows: pressure P = 30 to 40 kg, temperature of thermocompression bonding tool 400 to 500 ° C., bonding time 0.5 to 1.0.
Perform in seconds. After removing the organic film, nitrogen gas is applied to the inner lead portion so that oxidation of the surface of the inner lead 11 does not progress until the outer lead bonding.
Spray at NL / min.

The present invention can be applied to devices other than the TABinQFP type semiconductor device.
Like a dual tape carrier package (DTCP), which is often used for C, it can be applied to a film carrier type semiconductor device in which leads are exposed only from two sides of the package.

[0034]

As described above, according to the present invention, T
Since the leads of the AB and the leads of the lead frame are fused and connected firmly by the resistance welding method, so-called open defects hardly occur, and an electrically and mechanically stable package structure can be obtained. Furthermore, TA
Since the plating process on the portion where the lead B and the lead of the lead frame are fixed can be eliminated, a low-cost semiconductor device can be obtained.

Further, according to the method of manufacturing a semiconductor device of the present invention, the organic film for preventing oxidation of the lead of the lead frame is made of T.
By removing by heat treatment immediately before connection with the AB lead, plating can be eliminated on the portion where the TAB lead and the lead frame lead are fixed, even if conventional equipment is used. Is obtained.

[Brief description of the drawings]

FIG. 1 is a plan view of a first embodiment of the present invention in the order of manufacturing steps.

FIG. 2 is a sectional view of the embodiment of FIG. 1 in the order of manufacturing steps.

FIG. 3 is a sectional view of the projection 17 in FIG. 2 in the order of the manufacturing process.

FIG. 4 is a sectional view showing another manufacturing step in order of the projection 17 of FIG. 2;

FIG. 5 is a sectional view of still another manufacturing step of the protrusion of FIG. 2;

FIG. 6 is a perspective view illustrating a shape of a protrusion 17 of FIG. 2;

7 is a sectional view of the embodiment of FIG. 1 in the order of the manufacturing process.

FIG. 8 is a sectional view of a second embodiment of the present invention in the order of manufacturing steps.

FIG. 9 is a sectional view of a conventional semiconductor device in the order of manufacturing steps.

FIG. 10 is a sectional view of a conventional semiconductor device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 IC element 2 electrode 3 ILB lead 4 OLB lead 5 Suspender 6 Film carrier tape 7 Sprocket hole 8 Device hole 9 OLB hole 10 Pad 11 Inner lead 12 Outer lead 13 Island 14 OLB part 15 Lead frame 16 ILB part 17 Projection part 18 Adhesion Agent 19 Resin 20, 21 Welding electrode 22 Power supply 23, 24 Resist 25, 26 Mold 27 Thermocompression bonding tool 28 Bonding stage 29 Plating

Claims (5)

(57) [Claims] 1. A method of manufacturing a semiconductor device in which an outer lead bonding lead of a film carrier semiconductor device is bonded to an inner lead of a lead frame, wherein a protrusion is formed on the outer lead bonding lead, and the protrusion is formed on the inner lead. And bonding by an electric resistance welding method in contact with the semiconductor device. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the protrusions of the outer lead bonding leads are formed by an electroplating method, a chemical etching method, or a press working method. 3. A method of manufacturing a semiconductor device in which outer lead bonding is performed on an inner lead of a lead frame in which an outer lead bonding lead of a film carrier semiconductor device is covered with an organic film, a step of removing the organic film of the inner lead. Bonding the outer lead bonding leads by a thermocompression bonding method. 4. The method of manufacturing a semiconductor device according to claim 3, wherein the inner lead of the lead frame covered with the organic film is pressed against a heated tool to remove the organic film. 5. The method of manufacturing a semiconductor device according to claim 1, wherein plating treatment is not required for the inner leads of the lead frame.